Although it is well established that many medical conditions occurring in postmenopausal women are related to changes that have occurred in levels of reproductive hormones, especially estrogen, the details of the relationships between the levels of these hormones in symptomatic as compared to non-symptomatic women are not well understood. Similarly, there is little understanding of the physiological basis for side affects, reduced tolerance and noncompliance associated with hormone replacement therapy. A factor in this lack of understanding is the cost of assaying these hormones, which has kept them from being routinely monitored as a woman passes her reproductive phases. The applicant proposes to address this situation by developing a relatively low cost fiber optic sensor that will simultaneously measure estradiol, progesterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) in serum. The instrument will be designed for use in the physician's office and will provide results at least comparable to those obtained from clinical assay within minutes. During phase I, the plan is to examine the feasibility of combining the sensitivity of time resolved fluorescence assay using lanthanide chelates (that have been used in assays that have achieved sensitivity at the level of attamoles, 1 x 10 (-18) moles) with the speed and simplicity of a fiber optic biosensor.